The theory of the simple economy has shown us clearly the significance of human economy when the influence of power is eliminated. The economy arises whenever the means for the satisfaction of needs exist in economic proportions. Its object is to secure the highest utility that is possible under the pressure of this proportional-
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ity. From this practical end, applied reason has deduced all the manifold and complex rules of appraisal: the marginal law, the laws of supply, of demand, of costs, of common and specific attribution, and of capital appraisal. In each method there has been the presupposition that value is rigidly subjected to arithmetical processes, that the estimate of partial masses may be based on the multiplication of mass and the value of the unit. By trial and error, through thousands of years of experience, practical wisdom has formed the rules of computation which it adopts. An admirable structure has resulted, rich, yet rigidly self-contained. It is easy to see why the inquiring theoretical mind could not readily grasp its full significance.